Polymers of alpha-olefins prepared in the presence of heterogeneous catalyst systems, as for example, polypropylene prepared using a catalyst comprised of diethyl aluminum chloride and titanium trichloride, contain greater or lesser amounts of low-molecular-weight and amorphous components which, when taken alone, are viscous oils or soft, tacky solids. The presence of these alkane-soluble materials in the polymers leads to difficulties during their fabrication and to inferior physical properties of the finished item, and hence are almost always removed in commerical processes for the production of polypropylene.
In the past tertiary amine oxides, U.S. Pat. No. 3,288,773, have been reported as useful (c) components, supra, to reduce the alkane-soluble fraction produced during the polymerization process. Also, in British Pat. No. 1,000,348 heterocyclic amines and amine oxides are suggested for use as the (c) component of a catalyst system to obtain polymeric products of "unusually high crystallinity". So, too, in British Pat. No. 921,954 tertiary amine oxides and heterocyclic amine oxides are claimed as polymerization process additives to increase the crystalline polypropylene made using a process involving a Ziegler-type polymerization catalyst. In none of the above referred to patents, however, has the additive been claimed to reduce the alkane-soluble polymers to a point where no extraction would be necessary in the commercial process while still maintaining a commercially feasible yield of crystalline polymer. A polymer product containing about 2 percent or less of n-hexane soluble polymer would not require a separation step prior to use and hence would be economically advantageous.
Now it has been found that by using as the (c) component an amine oxide wherein sterically blocking groups are immediately adjacent to the nitrogen-oxygen bond, a poly alpha-olefin polymer substantially lower in alkane-solubles can be made in yields which are equal to or superior to those presently obtained in the better slurry-type processes.